Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Schedule of OP Unit Activity (Details) - shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in units)	108,862	239,619
OP Units issued upon redemption of Series C Units (in shares)	0	270,709

Noncontrolling Interest, Operating Partnership Units Redeemed For Common Stock

No definition available.

Name:	exr_NoncontrollingInterestOperatingPartnershipUnitsRedeemedForCommonStock
Namespace Prefix:	exr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration